Plating method and plating apparatus

ABSTRACT

The present invention relates to a plating method and a plating apparatus which can attain embedding of copper into fine interconnection patterns with use of a plating liquid having high throwing power and leveling properties, and which can make film thickness of a plated film substantially equal between an interconnection region and a non-interconnection region. A plating method comprises filling a plating liquid containing metal ions and an additive into a plating space formed between a substrate and an anode disposed closely to the substrate so as to face the substrate, and changing concentration of the additive in the plating liquid filled into the plating space during a plating process.

[0001] This application is a divisional application of U.S. Ser. No.09/955,115, filed Sep. 19, 2001, now allowed.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a plating method and a platingapparatus, and more particularly to a plating method and a platingapparatus for filling a metal such as copper (Cu) or the like into fineinterconnection patterns (trenches) on a semiconductor substrate.

[0004] 2. Description of the Related Art

[0005] Aluminum or an aluminum alloy has generally been used as amaterial for forming interconnect circuits on semiconductor substrates.As integrated density has increased in recent years, there is a demandfor usage of a material having a higher conductivity as an interconnectmaterial. It has been proposed to plate a substrate having interconnectpattern trenches thereon to fill the trenches with copper or its alloy.

[0006] There are known various processes including CVD (chemical vapordeposition), sputtering, and the like to fill interconnect patterntrenches with copper or its alloy. However, the CVD process is costlyfor forming copper interconnections, and the sputtering process fails toembed copper or its alloy in interconnect pattern trenches when theinterconnect pattern trenches have a high aspect ratio, i.e., a highratio of depth to width. A plating process is most effective to deposita metal layer of copper or its alloy on a substrate to form copperinterconnections thereon.

[0007] Various processes are available for plating semiconductorsubstrates with copper. These include a process of immersing a substratein a plating liquid held at all times in a plating tank, referred to asa cup-type or dipping-type process; a process of holding a platingliquid in a plating tank only when a substrate, to be plated, issupplied to the plating tank; an electric plating process for plating asubstrate with a potential difference; and an electroless platingprocess for plating a substrate with no potential difference.

[0008] In carrying out filling of fine interconnect patterns with copperby electric copper-plating using a copper sulfate solution as a platingliquid, it is required to perform a plating process with high throwingpower and high leveling properties. With a view to meeting thisrequirement, it is generally known to add to the plating liquid acompound called an additive.

[0009] Such an additive, generally in use, includes:

[0010] sulfur compounds called “carrier”, which grow crystal nuclei allover a plated surface, thereby promoting deposition of finer particles;

[0011] polymers which increase over-voltage of copper deposition,thereby enhancing throwing power; and

[0012] nitrogen compounds called “leveler”, which adhere to convexportions, where plating preferentially grows, to thereby increaseover-voltage and retard copper deposition at the convex portions,thereby providing a flat plated layer.

[0013] However, when filling fine interconnect patterns with copper byelectric copper-plating is conducted by using a plating liquid which,due to use of the above additives, has enhanced throwing power andleveling properties, there occurs a phenomena that a film thickness ofan interconnection region of a substrate becomes thicker than a filmthickness of a non-interconnection region. Unevenness in film thicknessis not a problem in filling the interconnection region with copper;however, unevenness makes it difficult to obtain a flat surface byperforming later CMP (chemical mechanical polishing) processing.

[0014] A plating treatment of a substrate for filling interconnectpattern trenches with a metal, such as copper or its alloy, may becarried out by using a plating apparatus as shown in FIG. 30. As shownin FIG. 30, a substrate W and an anode 302 are disposed in parallel,facing each other, in a plating tank 301 accommodating a plating liquid300. Plating is conducted by flowing a plating current i between thesubstrate W and the anode 302. A film thickness h of a plated filmformed at a certain point on a surface of the substrate W isproportional to a product of a plating current value and energizationtime. The plating current value in FIG. 30 is defined by the followingformula (1):

i=E/(R 1+R 2+R 3+R 4)  (1)

[0015] In the above formula (1), E represents power source voltage, R1anodic polarization resistance, R2 resistance of the plating liquid 300,R3 substrate (cathodic) polarization resistance, and R4 sheet resistanceof the substrate W at the certain point. The anodic polarizationresistance R1 and the substrate polarization resistance R3 areinterfacial resistances of the anode 302 and of the substrate W,respectively, and change with concentration of an additive or of theplating liquid. The resistance R2 of the plating liquid 300 isproportional to a distance between the anode 302 and the substrate(cathode) W.

[0016] An electric supply to the substrate W is made via a cathodeelectrode 303 which is generally connected to a peripheral end of thesubstrate W. Accordingly, the sheet resistance R4 at a point increasesas a distance from the peripheral end of the substrate W increases,i.e., as the point comes near to center P of the substrate W. Therefore,the plating current value on an inner central side of the substrate W issmaller than that on an outer peripheral side (see the above formula(1)), whereby it is likely that film thickness becomes smaller on theinner central side as compared to the outer peripheral side. There hasthus been a problem in conventional plating apparatuses that a platedfilm having a uniform film thickness over an entire substrate surface isdifficult to form. Especially when an LSI interconnection is formed byplating, a small thickness, generally 50-200 nm, of a seed layer of thesubstrate (Si substrate) makes the sheet resistance R4 considerablylarger. Such a large sheet resistance R4 has a larger influence on filmthickness.

SUMMARY OF THE INVENTION

[0017] The present invention has been made in view of the abovedrawbacks in the related art. It is therefore a first object of thepresent invention to provide a plating method and a plating apparatuswhich can attain embedding of copper into fine interconnect patternswith use of a plating liquid having high throwing power and levelingproperties, and which can make film thickness of a plated filmsubstantially equal between an interconnection region and anon-interconnection region, thereby facilitating later CMP processing.

[0018] It is a second object of the present invention to provide aplating apparatus and a plating method which can form a plated filmhaving a more uniform film thickness over an entire surface of asubstrate.

[0019] In order to achieve the first object, the present inventionprovides a plating method, comprising: filling a plating liquidcontaining metal ions and an additive into a plating space formedbetween a substrate and an anode disposed closely to the substrate so asto face the substrate; and changing concentration of an additive in theplating liquid filled into the plating space during a plating process.

[0020] In the course of plating of a substrate, concentration of anadditive in a plating liquid filled into a plating space formed betweenthe substrate and an anode gradually decreases with duration of theplating due to take-in of the additive within deposited metal film andoxidation degradation at the anode. The change of additive concentrationis larger in cases where {circle over (1)} plating of a substrate is bya close-to-anode plating where an amount of plating liquid itself issmall, {circle over (2)} introduction of a plating liquid into theplating space is conducted only before plating, and not conducted duringplating (batch-wise introduction), and {circle over (3)} a platingliquid is introduced intermittently during plating. The concentrationchange of the plating liquid is larger when, during a plating process,an additional solution or a plating liquid containing a differentconcentration of additive is separately introduced into the platingspace with a separate liquid introduction device.

[0021] By thus changing additive concentration of a plating liquidfilled into a plating space during a plating process, unevenness inplated film thickness between an interconnection region and anon-interconnection region is reduced or corrected.

[0022] It is not fully clarified by what mechanism a difference in filmthickness between the interconnection and non-interconnection regions iscorrected by making a change in the additive concentration, during theplating process, of the plating liquid filled into the plating space.Anyway, in general, the difference in film thickness can be effectivelycorrected when concentration of an additive decreases during the platingprocess; when concentration of a particular additive, especially aplating-promoting additive called “brightener”, is set at a high value;or when content of an additive is significantly lowered by, for example,adsorption removal of the additive. The film-thickness difference inquestion is considered to be produced at a middle or later stage of theplating process when filling metal into fine interconnect trenches hasalmost been completed. Accordingly, making a change in additiveconcentration of a plating liquid at a middle or later stage of platingis more effective than that at an initial stage when filling metal intointerconnect trenches is in progress.

[0023] Concentration of an additive in a plating liquid can be adjustedby intermittently supplying the plating liquid into a plating space.

[0024] Additive concentration can also be adjusted by supplementaryaddition of the additive to a plating space, or by removal of theadditive in a plating liquid.

[0025] The present invention also provides a plating apparatus,comprising: a substrate holder for holding a substrate so that a currentcan flow from a cathode to the substrate; an anode opposed to thesubstrate held by the substrate holder; and a plating liquid introducingdevice for introducing a plating liquid into a plating space formedbetween the substrate and the anode during a batch process or anintermittent process.

[0026] This apparatus can perform a plating treatment while changingconcentration of an additive in a plating liquid filled into the platingspace.

[0027] A plating liquid impregnation material may be provided in theplating space. The plating liquid impregnation material, e.g. syntheticfibers can adsorb and remove a particular additive component, e.g. aleveler, and thus is effective for reducing leveler concentration of aplating liquid.

[0028] Further, the plating apparatus may be provided with a liquidintroducing device for introducing into the plating space a liquidhaving a different additive concentration from that in the above platingliquid. The addition of the liquid (solution or plating liquid) havingthe different additive concentration makes it possible to arbitrarilycontrol, during a plating process, change of additive concentration inplating liquid filled into the plating space formed between thesubstrate and the anode. For example, addition of a liquid having ahigher leveler concentration, during a plating process, can correct afilm-thickness difference.

[0029] The plating apparatus may also be provided with a temperatureadjusting device for adjusting a temperature of plating liquid in theplating space. Since adsorption reaction, which occurs on the aboveplating liquid impregnation material is highly temperature-dependent,use of a higher plating liquid temperature generally increasesadsorption capacity of the plating liquid impregnation material.

[0030] In order to achieve the second object, the present inventionprovides a plating apparatus, comprising: a substrate holder for holdinga substrate so that a current can flow from a cathode to the substrate;an anode opposed to the substrate held by the substrate holder; and amoving device for moving a portion of the substrate facing the anode insuch a state that an inner central portion of a surface of the substratefaces the anode for a longer time than does an outer peripheral portionof the surface of the substrate.

[0031] This plating apparatus can make energization time of a platingcurrent to the inner central portion of the surface of the substratelonger than energization time of the plating current to the outerperipheral portion of the surface of the substrate, thereby makingproducts of electric current values and energization times of theelectric current, at various points of the substrate, equal over anentire surface of the substrate. This enables formation of a plated filmhaving a uniform film thickness over the entire surface of thesubstrate.

[0032] The moving device may comprise a substrate-rotating device forrotating the substrate, an anode-rotating device for rotating the anode,or an anode-translating device for translating the anode.

[0033] The present invention also provides another plating apparatuscomprising: a substrate holder for holding a substrate so that a currentcan flow from a cathode to the substrate; and an anode opposed to thesubstrate held by the substrate holder, wherein a distance between theanode and an inner central portion of a surface of the substrate issmaller than a distance between the anode and an outer peripheralportion of the surface of the substrate.

[0034] This apparatus can make resistance of a plating liquid at theinner central portion of the substrate smaller than that at the outerperipheral portion of the surface of the substrate, thereby making anelectric current value more equal at the inner central portion of thesurface of the substrate to that at the outer peripheral portion of thesurface of the substrate, whereby film thickness of plated film formedon the substrate can be made uniform over an entire surface of thesubstrate.

[0035] The present invention further provides a yet another platingapparatus comprising: a substrate holder for holding a substrate so thata current can flow from a cathode to the substrate; an anode opposed tothe substrate held by the substrate holder; and a distance changingdevice for changing a distance between the substrate and the anode afterinitiation of plating.

[0036] At initiation of plating, a potential gradient on an innercentral side of a surface of the substrate is higher than a potentialgradient on an outer peripheral side of the surface of the substrate,whereby a larger amount of plated film is formed on the inner centralside of the surface of the substrate. This situation can be reversedaccording to this apparatus, by later making a distance between thesubstrate and the anode larger. As a result, a plated film having auniform film thickness over an entire surface of the substrate can beobtained.

[0037] The present invention also provides a plating method, comprising:disposing a substrate and an anode in such a state that the substratefaces the anode; flowing a current between the substrate and the anodewhile supplying a plating liquid therebetween; and moving a portion ofthe substrate facing the anode in such a state that an inner centralportion of a surface of the substrate faces the anode for a longer timethan does an outer peripheral portion of the surface of the substrate.

[0038] The present invention also provides another plating method,comprising: disposing a substrate and an anode in a state that thesubstrate faces the substrate; and flowing a current between thesubstrate and the anode while supplying a plating liquid therebetween,wherein a distance between the anode and an inner central portion of asurface of the substrate is smaller than a distance between the anodeand an outer peripheral portion of the surface of the substrate.

[0039] The present invention further provides yet another platingmethod, comprising: disposing a substrate and an anode in a state thatthe substrate faces the anode; flowing a current between the substrateand the anode while supplying a plating liquid therebetween; andchanging a distance between the substrate and the anode after initiationof plating.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040]FIGS. 1A to 1C are sectional views showing an example of a processfor performing plating by a plating apparatus and a plating method ofthe present invention;

[0041]FIG. 2 is a plan view showing an entire plating apparatusaccording to a first embodiment of the present invention;

[0042]FIG. 3 is a plan view showing a plating unit;

[0043]FIG. 4 is a sectional view taken along line A-A of FIG. 3;

[0044]FIG. 5 is an enlarged sectional view of a substrate holder and acathode portion;

[0045]FIG. 6 is a front view of FIG. 3;

[0046]FIG. 7 is a right side view of FIG. 3;

[0047]FIG. 8 is a rear view of FIG. 3;

[0048]FIG. 9 is a left side view of FIG. 3;

[0049]FIG. 10 is a front view showing a pre-coating/recovering arm;

[0050]FIG. 11 is a plan view of the substrate holder;

[0051]FIG. 12 is a sectional view taken along line B-B of FIG. 11;

[0052]FIG. 13 is a sectional view taken along line C-C of FIG. 11;

[0053]FIG. 14 is a plan view of the cathode portion;

[0054]FIG. 15 is a sectional view taken along line D-D of FIG. 14;

[0055]FIG. 16 is a plan view of an electrode arm;

[0056]FIG. 17 is a longitudinal sectional front view of FIG. 16;

[0057]FIG. 18 is a sectional view taken along line E-E of FIG. 16;

[0058]FIG. 19 is an enlarged view showing a part of FIG. 18 in anenlarged manner;

[0059]FIG. 20 is a plan view of a state in which a housing of anelectrode portion of the electrode arm has been removed;

[0060]FIG. 21 is a longitudinal sectional front view of an electrode armcontaining a substrate holder according to a second embodiment of thepresent invention;

[0061]FIG. 22 is a plan view showing a relationship between a substrateand an anode according to the second embodiment of the presentinvention;

[0062]FIG. 23 is a plan view of an electrode arm according to a thirdembodiment of the present invention;

[0063]FIG. 24 is a plan view showing a relationship between a substrateand an anode according to the third embodiment of the present invention;

[0064]FIG. 25 is a pattern diagram showing a relationship between asubstrate and an electrode portion according to a fourth embodiment ofthe present invention;

[0065]FIG. 26 is a pattern diagram showing a relationship between asubstrate and an electrode portion according to a fifth embodiment ofthe present invention;

[0066]FIG. 27A is a pattern diagram showing a relationship between asubstrate and an anode at initiation of plating according to a sixthembodiment of the present invention;

[0067]FIG. 27B is a pattern diagram showing a relationship between thesubstrate and the anode at completion of plating according to the sixthembodiment of the present invention;

[0068]FIG. 28A is an isoelectric line diagram showing a state of anelectric field between the anode and the substrate in the relationshipof FIG. 27A;

[0069]FIG. 28B is an isoelectric line diagram showing a state of anelectric field between the anode and the substrate in the relationshipof FIG. 27B;

[0070]FIG. 29 is a sectional view of a face-down type plating apparatusaccording to a seventh embodiment of the present invention; and

[0071]FIG. 30 is a view showing a circuit typically formed by aconventional plating apparatus and its plating treatment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0072] An embodiment of the present invention will be described belowwith reference to the drawings. A substrate plating apparatus accordingto this embodiment is used to apply copper electroplating onto a surfaceof a semiconductor substrate, thereby obtaining a semiconductorapparatus having interconnects comprising a copper layer formed thereon.A plating process will be explained with reference to FIGS. 1A through1C.

[0073] As shown in FIG 1A, an oxide film 2 of SiO₂ is deposited on aconductive layer 1 a on a semiconductor substrate 1 on whichsemiconductor devices are formed. A contact hole 3 and a trench 4 for aninterconnect are formed by performing lithography and etchingtechnology. A barrier layer 5 of TiN or the like is formed on the oxidefilm 2, and then a seed layer 7, as an electric supply layer forelectroplating, is formed on the barrier layer 5.

[0074] Then, as shown in FIG. 1B, a surface of the seed layer 7 iscoated with copper by performing copper electroplating to deposit aplated copper film 6 on the oxide film 2, thus filling the contact hole3 and the trench 4 with copper. Thereafter, the plated copper film 6 onthe oxide film 2 is removed by performing chemical mechanical polishing(CMP), thus causing the plated copper film 6 in the contact hole 3 andthe trench 4 to lie flush with the oxide film 2. In this manner, aninterconnect composed of copper 6 is formed as shown in FIG 1C.

[0075]FIG. 2 is a plan view showing an entire plating apparatus for asubstrate according to an embodiment of the present invention. As shownin FIG. 2, this plating apparatus has a rectangular facility whichhouses therein two loading/unloading units 10 for housing a plurality ofsubstrates W therein, two plating units 12 for performing platingtreatment and treatment incidental thereto, a transfer robot 14 fortransferring substrates W between the loading/unloading units 10 and theplating units 12, and plating liquid supply equipment 18 having aplating liquid tank 16.

[0076] The plating liquid used in this embodiment contains the followingadditives: a sulfur-containing compound, such as thiourea and acrylicthiourea, as a carrier (brightener); polyether, polyethylene glycol ortheir derivatives as a polymer; and a nitrogen compound having apositive charge, such as polyamine or dyestuffs, as a leveler. Ofcourse, the present invention is not limited to use of these additives.

[0077] Each plating unit 12, as shown in FIG. 3, is provided with asubstrate treatment section 20 for performing plating treatment andtreatment incidental thereto, and a plating liquid tray 22 for storing aplating liquid is disposed adjacent to the substrate treatment section20. There is also provided an electrode arm 30 having an electrodeportion 28 which is held at a front end of an arm 26 swingable about arotating shaft 24, and which is swung between the substrate treatmentsection 20 and the plating liquid tray 22. Furthermore, apre-coating/recovering arm 32, and fixed nozzles 34, for ejecting purewater or a chemical liquid such as ion water along with a gas or thelike toward a substrate, are disposed laterally of the substratetreatment section 20. In this embodiment, three fixed nozzles 34 aredisposed, and one of them is used for supplying pure water.

[0078] The substrate treatment section 20, as shown in FIGS. 4 and 5,has a substrate holder 36 for holding a substrate W with its surface tobe plated facing upwardly, and a cathode portion 38 located above thesubstrate holder 36 so as to surround a peripheral portion of thesubstrate holder 36. Further, a substantially cylindrical bottomed cup40 surrounding a periphery of the substrate holder 36, for preventingscatter of various chemical liquids used during treatment, is providedso as to be vertically movable by an air cylinder 42.

[0079] The substrate holder 36 is adapted to be raised and lowered bythe air cylinder 42 between a lower substrate transfer position A, anupper plating position B, and a pre-treatment/cleaning position Cbetween these positions A and B, as shown in FIG. 5. The substrateholder 36 is also adapted to rotate at an arbitrary acceleration and anarbitrary velocity integrally with the cathode portion 38 by a rotatingmotor 46 and a belt 48 (see FIG. 4). A substrate carry-in and carry-outopening 50 is provided in confrontation with substrate transfer positionA in a frame side surface of the plating unit 12 facing the transferrobot 14, as shown FIG. 7. When the substrate holder 36 is raised toplating position B, a seal member 90 and cathode electrodes 88 (to bedescribed below) of the cathode portion 38 are brought into contact witha peripheral edge portion of substrate W held by the substrate holder36. On the other hand, the cup 40 has an upper end located below thesubstrate carry-in and carry-out opening 50, and when the cup 40ascends, the upper end of the cup 40 reaches a position above thecathode portion 38, thereby closing the substrate carry-in and carry-outopening 50, as shown by imaginary lines in FIG. 5.

[0080] The plating liquid tray 22 serves to wet a plating liquidimpregnation material 110 and an anode 98 (to be described later) of theelectrode arm 30 with a plating liquid, when plating has not beenperformed. As shown in FIG. 6, the plating liquid tray 22 is set to asize at which the plating liquid impregnation material 110 can beaccommodated, and the plating liquid tray 22 has a plating liquid supplyport and a plating liquid drainage port (not shown). A photo-sensor isattached to the plating liquid tray 22, and can detect brimming with theplating liquid in the plating liquid tray 22, i.e., overflow anddrainage. A bottom plate 52 of the plating liquid tray 22 is detachable,and a local exhaust port (not shown) is installed around the platingliquid tray.

[0081] As shown in FIGS. 8 and 9, the electrode arm 30 is verticallymovable by a motor 54 and a ball screw, not shown, and swingable betweenthe plating liquid tray 22 and the substrate treatment section 20 by amotor 56.

[0082] As shown in FIG. 10, the pre-coating/recovering arm 32 is coupledto an upper end of a vertical support shaft 58. Thepre-coating/recovering arm 32 is swingable by a rotary actuator 60 andis also vertically moveable by an air cylinder 62 (see FIG. 7). Thepre-coating/recovering arm 32 supports a pre-coating nozzle 64 fordischarging a pre-coating liquid, on its free end, and a plating liquidrecovering nozzle 66 for recovering plating liquid, on a portion closerto its proximal end. The pre-coating nozzle 64 is connected to a syringethat is actuatable by an air cylinder, for example, for intermittentlydischarging a pre-coating liquid from the pre-coating nozzle 64. Theplating liquid recovering nozzle 66 is connected to a cylinder pump oran aspirator, for example, to draw plating liquid on the substrate viathe plating liquid recovering nozzle 66.

[0083] As shown in FIGS. 11 through 13, the substrate holder 36 has adisk-shaped substrate stage 68 and six vertical support arms 70 disposedat spaced intervals on a circumferential edge of the substrate stage 68for holding a substrate W in a horizontal plane on respective uppersurfaces of the support arms 70. A positioning plate 72 is mounted on anupper end one of the support arms 70 for positioning the substrate bycontacting an end face of the substrate. A pressing finger 74 isrotatably mounted on an upper end of the support arm 70 which ispositioned opposite to the support arm 70 having the positioning plate72, for abutting an end face of the substrate W and pressing thesubstrate W against the positioning plate 72 when rotated. Chuckingfingers 76 are rotatably mounted on upper ends of the remaining foursupport arms 70 for pressing the substrate W downwardly and gripping acircumferential edge of the substrate W.

[0084] The pressing finger 74 and the chucking fingers 76 haverespective lower ends coupled to upper ends of pressing pins 80 that arenormally urged to move downwardly by coil springs 78. When the pressingpins 80 are moved downwardly, the pressing finger 74 and the chuckingfingers 76 are rotated radially inwardly into a closed position. Asupport plate 82 is disposed below the substrate stage 68 for engaginglower ends of the pressing pins 80 and pushing them upwardly.

[0085] When the substrate holder 36 is located in substrate transferposition A shown in FIG. 5, the pressing pins 80 are engaged and pushedupwardly by the support plate 82, so that the pressing finger 74 and thechucking fingers 76 rotate outwardly and open. When the substrate stage68 is elevated, the opening pins 80 are lowered under resiliency of thecoil springs 78, so that the pressing finger 74 and the chucking fingers76 rotate inwardly and close.

[0086] As shown in FIGS. 14 and 15, the cathode portion 38 comprises anannular frame 86 fixed to upper ends of vertical support columns 84mounted on a peripheral edge of the support plate 82 (see FIGS. 5 and13), a plurality of, six in this embodiment, cathode electrodes 88attached to a lower surface of the annular frame 86 and projectinginwardly, and an annular sealing member 90 mounted on an upper surfaceof the annular frame 86 in covering relation to upper surfaces of thecathode electrodes 88. The sealing member 90 is adapted to have an innerperipheral edge portion inclined inwardly downwardly and progressivelythinned, and to have an inner peripheral end suspending downwardly.

[0087] When the substrate holder 36 has ascended to plating position B,as shown in FIG. 5, the cathode electrodes 88 are pressed against aperipheral edge portion of substrate W held by the substrate holder 36for thereby causing electric current to flow through the substrate W. Atthe same time, an inner peripheral end portion of the seal member 90 isbrought into contact with an upper surface of the peripheral edge of thesubstrate W under pressure to seal its contact portion in a watertightmanner. As a result, plating liquid supplied onto an upper surface(surface to be plated) of the substrate W is prevented from seeping froman end portion of the substrate W, and the plating liquid is preventedfrom contaminating the cathode electrodes 88.

[0088] In the present embodiment, the cathode portion 38 is verticallyimmovable, but rotatably integrated with the substrate holder 36.However, the cathode portion 38 may be arranged such that it isvertically movable and the sealing member 90 is pressed against asurface, to be plated, of substrate W when the cathode portion 38 islowered.

[0089] As shown in FIGS. 16 through 20, the electrode head 28 of theelectrode arm 30 comprises a housing 94 coupled to a free end of theswing arm 26 through a ball bearing 92, a cylindrical support frame 96surrounding the housing 94, and an anode 98 fixed by having a peripheraledge portion thereof gripped between the housing 94 and the supportframe 96. The anode 98 covers an opening of the housing 94, which has asuction chamber 100 defined therein. In the suction chamber 100, thereis disposed a diametrically extending plating liquid introduction pipe104 connected to a plating liquid supply pipe 102 which extends from theplating liquid supply unit 18 (see FIG. 2), and held in abutment with anupper surface of the anode 98. A plating liquid discharge pipe 106communicating with the suction chamber 100 is connected to the housing94.

[0090] The plating liquid introduction pipe 104 is effective to supplyplating liquid uniformly to a surface, to be plated, of substrate W ifthe plating liquid introduction pipe 104 is of a manifold structure.Specifically, the plating liquid introduction pipe 104 has a platingliquid introduction passage 104 a extending continuously in itslongitudinal direction, and a plurality of plating liquid introductionports 104 b spaced at a given pitch along the plating liquidintroduction passage 104 a and extending downwardly therefrom incommunication therewith. The anode 98 has a plurality of plating liquidsupply ports 98 a defined therein at positions corresponding to theplating liquid introduction ports 104 b. The anode 98 also has a numberof vertically extending through holes 98 b defined therein over itsentire region. Plating liquid that is introduced from the plating liquidsupply pipe 102 into the plating liquid introduction pipe 104 flowsthrough the plating liquid introduction ports 104 b and the platingliquid supply ports 98 a to a plating space 99 (see FIG. 17) formedbetween the anode 98 and substrate W. The plating liquid discharge pipe106 is evacuated to discharge the plating liquid within the platingspace 99 formed between the anode 98 and the substrate W via the throughholes 98 b and the suction chamber 100 from the plating liquid dischargepipe 106.

[0091] Further, a liquid supply pipe 120 for separately introducing asolution or plating liquid, having a different additive concentrationfrom the plating liquid, into the plating space 99 formed between theanode 98 and the substrate W is connected to the housing 94. Byintroducing into the plating space 99 from the liquid supply pipe 120,during a plating process, a solution or plating liquid having adifferent additive concentration a change of additive concentration inplating liquid contained in the plating space 99 can arbitrarily becontrolled.

[0092] As shown in FIG. 17, the anode 98 is designed to havesubstantially the same size (diameter) as substrate W so that the anodecovers substantially an entire surface of the substrate W.

[0093] In order to suppress generation of slime, the anode 98 is made ofcopper containing 0.03 to 0.05% phosphorus (phosphorus copper). When theanode 98 is made of phosphorus copper, a black film is formed on asurface of the anode 98 as a plating process progresses. The black filmis made of a Cu⁺ complex containing phosphorus and Cl, and comprisesCu₂Cl₂.Cu₂O.Cu₃P, and the like. Since the black film suppresses a copperdisproportionation reaction, it is important to stably form the blackfilm on the surface of the anode 98 for a purpose of stabilizing theplating process. However, if the black film is dried and oxidized, andpeeled off the anode 98, then it tends to produce particles and causes achange in composition of a plating.

[0094] In this embodiment, a plating liquid impregnation material 110comprising a water retaining material and covering an entire surface ofthe anode 98 is attached to a lower surface of the anode 98. The platingliquid impregnation material 110 is impregnated with plating liquid towet the lower surface of the anode 98, thereby preventing a black filmfrom falling onto a plated surface of a substrate by drying andoxidizing, and simultaneously facilitating escape of air to an exteriorwhen the plating liquid is poured between the surface, to be plated, ofthe substrate and the anode 98.

[0095] Further, by attaching the plating liquid impregnation material110 to the anode 98 and contacting the material 110 with plating liquidpoured into the plating space 99 between a surface, to be plated, ofsubstrate W and the anode 98, a particular additive component, e.g. aleveler, can be adsorbed and removed by the plating liquid impregnationmaterial 110. Use of the plating liquid impregnation material is thuseffective for reducing leveler concentration of plating liquid in theplating space 99.

[0096] The plating liquid impregnation material 110 has both functionsof retaining liquid and passing liquid therethrough, and has excellentchemical resistance. Specifically, the plating liquid impregnationmaterial 110 has endurance against an acid plating liquid includingsulfuric acid having high concentration. The plating liquid impregnationmaterial 110 comprises, for example, a woven fabric of polypropylene toprevent elution of impurities in a sulfuric acid solution from having abad influence on plating efficiency (plating speed, resistivity andfilling characteristics). The plating liquid impregnation material 110may comprise at least one material of polyethylene, polyester, polyvinylchloride, Teflon, polyvinyl alcohol, polyurethane, and derivatives ofthese materials, other than polypropylene. Nonwoven fabric or asponge-like structure may be used in place of woven fabric. Porousceramics and sintered polypropylene made of alumina and SiC, and thelike, are available.

[0097] That is, many fixing pins 112 each having a head portion at alower end thereof are arranged such that the head portion is provided inthe plating liquid impregnation material 110 so as not to be releasableupwardly, and a shaft portion of the fixing pin pierces an interior ofthe anode 98. Also, the fixing pins 112 are urged upwardly by U-shapedplate springs 114, whereby the plating liquid impregnation material 110is brought into close contact with the lower surface of the anode 98 byresilient force of the plate springs 114 and is attached to the anode98. With this arrangement, even when thickness of the anode 98 graduallydecreases with progress of plating, the plating liquid impregnationmaterial 110 can be reliably brought into close contact with the lowersurface of the anode 98. Thus, air can be prevented from enteringbetween the lower surface of the anode 98 and the plating liquidimpregnation material 110 so as to not cause poor plating.

[0098] Incidentally, columnar pins made of PVC (polyvinyl chloride) orPET and having a diameter of, for example, about 2 mm may be arrangedfrom an upper surface side of the anode 98 so as to pierce the anode,and an adhesive may be applied to a front end surface of each of thepins projecting from the lower surface of the anode to fix the anode tothe plating liquid impregnation material 110. When the plating liquidimpregnation material 110 has a sufficient strength, such as thatassociated with ceramics, the anode 98 may be placed on the platingliquid impregnation material fixed to a supporter without using pins forfixing the impregnation material. It is not necessary to bring intoclose contact the plating liquid impregnation material 110 with theanode 98, and a plating liquid may be filled into a gap between theplating liquid impregnation material and the anode.

[0099] When the substrate holder 36 is in plating position B (see FIG.5), the electrode head 28 is lowered until a gap between substrate Wheld by the substrate holder 36 and the plating liquid impregnationmaterial 110 becomes about 0.5 to 3 mm, for example. Then, platingliquid is supplied from the plating liquid supply pipe 102 to fill a gapbetween an upper surface, to be plated, of the substrate W and the anode98 while impregnating the plating liquid impregnation material 110 withplating liquid, thereby plating the upper surface of the substrate W.

[0100] As shown in FIG. 4, stopper bars 116 are erected outwardly of thesupport columns 84 supporting the cathode portion 38. As shown in FIGS.16 and 17, protrusions 96 a provided on a periphery of the support frame96 are brought into contact with upper surfaces of the stopper bars 116,whereby descent of the electrode portion 28 is controlled.

[0101] A plating process carried out by the substrate plating apparatusaccording to the above embodiment will be described below.

[0102] First, a substrate W, to be plated, is removed from one of theloading/unloading units 10 by the transfer robot 14, and transferred,with a surface to be plated oriented upwardly, through substratecarry-in and carry-out opening 50 defined in a side panel, into one ofthe plating units 12. At this time, substrate holder 36 is in lowersubstrate transfer position A. After a hand of the transfer robot 14 hasreached a position directly above substrate stage 68, the hand of thetransfer robot 14 is lowered to place the substrate W onto support arm70. The hand of the transfer robot 14 is then retracted through thesubstrate carry-in and carry-out opening 50.

[0103] After the hand of the transfer robot 14 is retracted, cup 40 iselevated. Then, the substrate holder 36 is lifted from substratetransfer position A to pre-treating/cleaning position C. As thesubstrate holder 36 ascends, the substrate W placed on support arms 70is positioned by positioning plate 72 and pressing finger 74, and thenreliably gripped by fixing fingers 76.

[0104] On the other hand, electrode head 28 of electrode arm 30 is nowin a normal position over plating liquid tray 22, and plating liquidimpregnation material 110 or anode 98 is positioned in the platingliquid tray 22. At the same time that the cup 40 ascends, plating liquidstarts being supplied to the plating liquid tray 22 and the electrodehead 28. Until a step of plating the substrate W is initiated, newplating liquid is supplied, and plating liquid discharge pipe 106 isevacuated to replace plating liquid in the plating liquid impregnationmaterial 110 and remove air bubbles from the plating liquid in theplating liquid impregnation material 110. When ascending movement of thecup 40 is completed, the substrate carry-in and carry-out opening 50 inthe side panel is closed by the cup 40, thereby isolating an atmosphereinterior of the side panel and an atmosphere exterior of the side panelfrom each other.

[0105] When the cup 40 is elevated, a pre-coating step is initiated.Specifically, the substrate holder 36 that has received the substrate Wis rotated, and pre-coating/recovering arm 32 is moved from a retractedposition to a position confronting the substrate W. When rotationalspeed of the substrate holder 36 reaches a setting value, pre-coatingnozzle 64 mounted on a tip end of the pre-coating/recovering arm 32intermittently discharges a pre-coating liquid which comprises a surfaceactive agent, for example, toward the surface to be plated of thesubstrate W. At this time, since the substrate holder 36 is rotating,the pre-coating liquid spreads all over the surface, to be plated, ofthe substrate W. Then, the pre-coating/recovering arm 32 is returned tothe retracted position, and rotational speed of the substrate holder 36is increased to spin the pre-coating liquid off and dry the surface, tobe plated, of the substrate W.

[0106] After completion of the pre-coating step, a plating step isinitiated. First, rotation of the substrate holder 36 is stopped, orrotational speed thereof is reduced to a preset rotational speed forplating. In this state, the substrate holder 36 is lifted to platingposition B. Then, a peripheral edge of the substrate W is brought intocontact with cathode electrodes 88, when it is possible to cause anelectric current to flow, and at the same time, sealing member 90 ispressed against an upper surface of the peripheral edge of the substrateW, thereby sealing the peripheral edge of the substrate W in awater-tight fashion.

[0107] Based on a signal indicating that the precoating step for loadedsubstrate W is completed, the electrode arm 30 is swung in a horizontaldirection to displace the electrode head 28 from a position over theplating liquid tray 22 to a position over a plating position. After theelectrode head 28 reaches this position, the electrode head 28 islowered toward cathode portion 38. At this time, the plating liquidimpregnation material 110 does not contact with the surface, to beplated, of the substrate W, but is held closely to the surface, to beplated, of the substrate W at a distance ranging from 0.5 mm to 3 mm.When descent of the electrode head 28 is completed, a plating current isapplied, and plating liquid is supplied from plating liquid supply pipe102 into the electrode head 28, and then from plating liquid supplyports 98 a through the anode 98 to the plating liquid impregnationmaterial 110.

[0108] When supply of the plating liquid continues, the plating liquidcontaining copper ions, which has seeped out of the plating liquidimpregnation material 110, is filled into a gap between the platingliquid impregnation material 110 and the surface, to be plated, of thesubstrate W so that copper plating is performed on the surface, to beplated, of the substrate.

[0109] After supplying a predetermined amount of plating liquid,introduction of the plating liquid is stopped, and the substrate holder36 is rotated at a low speed so that the plating liquid can be suppliedevenly to the surface, to be plated, of the substrate. Rotation of thesubstrate holder is continued e.g. for 5 minutes. Plating liquid used inthis embodiment contains an additive concentration of e.g. 1.0 mL/L, andis used in an amount of e.g. 50 mL according to a volume of platingspace 99. The additive concentration decreases with progress of theplating process, whereby unevenness in a plated film thickness betweenan interconnection region and an non-interconnection region iscorrected.

[0110] More specifically, during plating of the substrate, the additiveconcentration gradually decreases with progress of plating due totake-in of the additive within a deposited metal film and oxidationdegradation at the anode 98. A change (decrease) in additiveconcentration of plating liquid contained in the plating space 99 formedbetween the substrate and the anode 98 is large in such cases as thisembodiment, where plating of the substrate is by a close-to-anodeplating wherein an amount of plating liquid itself in the plating space99 is small, and introduction of plating liquid into the plating space99 is conducted only before plating, and not conducted during theplating process. This effectively corrects unevenness in the plated filmthickness between the interconnection region and the non-interconnectionregion. Further, use of the plating liquid impregnation material 110 canadsorb and remove a particular additive compound, e.g. a leveler,thereby more effectively reducing a leveler concentration of platingliquid contained in the plating space 99.

[0111] Though in this embodiment introduction of plating liquid into theplating space 99 is conducted only before a plating process (batch-wiseintroduction), the plating liquid may be introduced intermittentlyduring the plating process. Further, by separately introducing duringthe plating process, a solution or plating liquid having a differentadditive concentration, into the plating space 99 from the liquid supplypipe 120, a change of additive concentration in plating liquid containedin the plating space 99 can be made larger.

[0112] When the plating treatment is completed, the electrode arm 30 israised and then swung to return to a position above the plating liquidtray 22 and to lower to an ordinary position. Then, thepre-coating/recovering arm 32 is moved from a retreat position to theposition confronting the semiconductor substrate W, and lowered torecover a remainder of plating liquid on the substrate W via platingliquid recovering nozzle 66. After recovery of the remainder of theplating liquid is completed, the pre-coating/recovering arm 32 isreturned to the retreat position, and pure water is supplied from fixednozzle 34 for supplying pure water toward a central portion of thesubstrate W for rinsing a plated surface of the substrate. At the sametime, the substrate holder 36 is rotated at an increased speed toreplace plating liquid on the surface of the substrate W with purewater. Rinsing the substrate W in this manner prevents splashing platingliquid from contaminating the cathode electrodes 88 of the cathodeportion 38 during descent of the substrate holder 36 from platingposition B.

[0113] After completion of rinsing, a washing with water step isinitiated. That is, the substrate holder 36 is lowered from platingposition B to pre-treatment/cleaning position C. Then, while pure wateris supplied from the fixed nozzle 34, the substrate holder 36 and thecathode portion 38 are rotated to perform washing with water. At thistime, the seal member 90 and the cathode electrodes 88 can also becleaned, simultaneously with substrate W, by virtue of pure waterdirectly supplied to the cathode 38, or pure water scattered from asurface of the substrate W.

[0114] After washing with water is completed, a drying step isinitiated. That is, supply of pure water from the fixed nozzle 34 isstopped, and a rotational speed of the substrate holder 36 and thecathode portion 38 is further increased to remove pure water on thesurface of the substrate W by centrifugal force, and to dry the surfaceof the substrate W. The seal member 90 and the cathode electrodes 88 arealso dried at the same time. Upon completion of drying, rotation of thesubstrate holder 36 and the cathode portion 38 is stopped, and thesubstrate holder 36 is lowered to substrate transfer position A. Thus,gripping of the substrate W by the fixing fingers 76 is released, andthe substrate W is just placed on upper surfaces of the support arms 70.At the same time, the cup 40 is also lowered.

[0115] All steps including the plating step, the pre-treating stepaccompanying the plating step, the cleaning step, and the drying stepare now finished. The transfer robot 14 inserts its hand through thesubstrate carry-in and carry-out opening 50 and to a position beneaththe substrate W, and raises the hand to receive processed substrate Wfrom the substrate holder 36. Then, the transfer robot 14 returns theprocessed substrate W, received from the substrate holder 36, to one ofthe loading/unloading units 10.

[0116] This embodiment shows a case where plating is carried out at aconstant temperature. In this case, though additive concentration of theplating liquid decreases until the plating liquid impregnation material110 reaches adsorption saturation, this effect can no longer be expectedafter adsorption saturation. Accordingly, for example, a device foradjusting a temperature of plating liquid during a plating process, suchas a heater, may be provided around the anode 98 so as to graduallyraise a plating temperature in accordance with progress of a platingprocess, whereby adsorption capacity of the plating liquid impregnationmaterial 110 for an additive in the plating liquid can be enhanced. Itis also possible to utilize spontaneous temperature rising due to Jouleheat that generates during a plating process. In this case, aftercompletion of plating, the plating liquid impregnation material 110 maybe brought into contact with a low-temperature plating liquid to detachpart of an adsorbed additive. An additive excessively adsorbed due tohigh temperature can thus be detached.

[0117] Further, the plating apparatus may be arranged such that aplurality of plating liquids having different additive concentrationscan be introduced, through the plating liquid supply pipe 102, into thespace between a surface, to be plated, of a substrate and the anode 98.Plating may be conducted by using, at an initial stage of a platingprocess, a plating liquid having a proper additive concentration formetal filling into interconnections, and replacing the plating liquidwith other plating liquids having lower additive concentrations at amiddle or later stage of the plating process, thereby adjusting additiveconcentration of the plating liquid during the plating process.

[0118] Adjustment of additive concentration during a plating process mayalso be made by using, at an initial stage of a plating process, ananode that holds a plating liquid impregnation material impregnated witha plating liquid having a proper additive concentration for metalfilling, and using, at a middle or later stage of the plating process,an anode that holds a plating liquid impregnation material impregnatedwith a plating liquid having a lower additive concentration.

[0119] The following are results of various experiments which wereconducted to show technical effects attained by the plating treatmentaccording to this embodiment.

[0120] First, in order to examine a relationship between an amount ofplating liquid and filling properties, plating was conducted withvarious amounts of plating liquid under the following plating conditionsto determine additive concentration at initial, middle and later stagesof a plating process, a film-thickness difference betweeninterconnection and non-interconnection regions, and presence or absenceof voids in interconnections. The results are shown in Table 1.

[0121] Plating conditions:

[0122] Copper sulfate pentahydrate=225 g/L, Sulfuric acid=55 g/L,Chloride ion=60 mg/L, Additive=DMEC#40 (all manufactured byEBARA-UDYLITE CO., LTD.)

[0123] Temperature=25° C., Electric current density=20 mA/cm², Platingtime=5 min (average thickness of plated film: 2000 nm)

[0124] Impregnation material: not used TABLE 1 Amount of plating liquidand filling properties Amount of Plating 5 ml 50 ml 500 ml 1000 ml 5000ml liquid (ml/substrate) Measured additive Initial stage (0 min) 1.0 1.01.0 1.0 1.0 concentration Middle stage (2.5 min) 0 0 0.6 0.9 1.0 (ml/l)Later stage (5 min) 0 0 0.1 0.5 0.9 Film-thickness (=Interconnection 0100 400 1000 1800 difference region - (nm) Non-interconnection regionPresence of Found None None None None voids in interconnection

[0125] As can be seen from Table 1, use of a smaller amount of platingliquid results in a smaller difference in film thickness of a platedfilm between an interconnection region and a non-interconnection region,thereby providing a film-thickness distribution feasible for CMPprocessing. This is considered to be due to decrease in a brightenercomponent which is a main cause of the film-thickness difference. Table1 also shows that use of an extremely small amount of plating liquidresults in formation of voids in the interconnection, and thus is notpreferred. This may be due to shortage of the brightener component whichis a main factor for bottom-up growth in via holes, which is importantfor metal filling into fine interconnections.

[0126] Next, in order to examine a change of additive concentration withor without use of a plating liquid impregnation material, plating wasconducted under the following plating conditions to determine additiveconcentration at initial, middle and later stages of a plating process,a film-thickness difference between interconnection andnon-interconnection regions, and presence or absence of voids ininterconnections. The results are shown in Table 2.

[0127] Plating conditions:

[0128] Copper sulfate pentahydrate=225 g/L, Sulfuric acid=55 g/L,Chloride ion=60 mg/L, Additive=DMEC#40 (all manufactured byEBARA-UDYLITE CO., LTD.)

[0129] Temperature=25° C., Electric current density=20 mA/cm², Platingtime=5 min (average thickness of plated film: 2000 nm)

[0130] Impregnation material: PVA sponge (thickness: 4 mm), previousadditive-adsorption treatment not made

[0131] Amount of plating liquid: 1000 mL/substrate TABLE 2 Additiveadjustment by adsorption by impregnation material With Withoutimpregnation impregnation material material Measured additive Initialstage (0 min) 1.0 1.0 concentration Middle stage (2.5 min) 0.2 0.9(ml/l) Later stage (5 min) 0   0.5 Film-thickness (=Interconnection100-150 1000 difference (nm) region - Non-interconnection region)Presence of voids None None in interconnection

[0132] As can be seen from Table 2, by carrying out plating in thepresence of a plating liquid impregnation material havingadditive-adsorbing properties, additive concentration can be effectivelydecreased during the plating process, whereby plating can be achievedwith a smaller film-thickness difference and without formation of voidsin interconnections. This is considered to be due to the fact thatconcentration of a brightener, which is necessary for interconnectionfilling, is high at the initial stage of the plating process, whereas atthe middle or later stage of the plating process, the brightenerconcentration is lowered by adsorption by the plating liquidimpregnation material.

[0133] Further, multistage plating using plating liquids havingdifferent additive concentrations and normal plating using a singleplating liquid were conducted under the following plating conditions todetermine additive concentration at initial, middle and later stages ofthe plating process, a film-thickness difference between interconnectionand non-interconnection regions and presence or absence of voids ininterconnections. The results are shown in Table 3.

[0134] Plating conditions:

[0135] Copper sulfate pentahydrate=225 g/L, Sulfuric acid=55 g/L,Chloride ion=60 mg/L, Additive=DMEC#40 (all manufactured byEBARA-UDYLITE CO., LTD.)

[0136] Temperature=25° C., Electric current density=20 mA/cm², Platingtime=5 min (average thickness of plated film: 2000 nm)

[0137] Impregnation material: not used

[0138] Amount of plating liquid: 5000 mL/substrate, the additiveconcentration shown in Table 3 TABLE 3 Results of multistage platingMultistage plating(ml/l) 0-1.5 min: Concentration 1.0 1.5-3 min:Normal(Single Concentration 0.3 liquid) 3-5 min: Concentration:Concentration 0 1.0 ml/l Measured Initial stage 1.0 1.0 additive (0 min)concentration Middle stage 0.3 1.0 (ml/l) (2.5 min) Later stage 0   0.9(5 min) Film-thickness (=Interconnection 100-150 1800 differenceregion - (nm) Non- interconnection region) Presence of None None voidsin interconnection

[0139] As can be seen Table 3, by decreasing stepwise additiveconcentration of a plating liquid in accordance with progress of aplating process, a plated film having a small film-thickness difference,thus feasible for CMP processing, can be obtained.

[0140] As described hereinabove, according to this embodiment of thepresent invention, plating of a substrate can be performed with a smallfilm-thickness difference between the interconnection andnon-interconnection regions, which is feasible for later CMP processing,and without forming voids in the interconnections. This improves productyield, can simplify process steps and attains a considerable lowering ofproduction costs.

[0141]FIGS. 21 and 22 show a plating apparatus according to a secondembodiment of the present invention. FIG. 21 is a longitudinal sectionalfront view of an electrode arm containing a substrate holder, and FIG.22 is a plan view showing a relationship between a substrate and ananode.

[0142] According to the plating apparatus of this embodiment, a size(diameter) of anode 98 is designed to be smaller than a size (diameter)of substrate W, so that an area of the anode 98 becomes smaller than thearea of the substrate W. Further, a rotary motor 130 as ananode-rotating device is provided at an upper end of electrode portion28, so that the anode 98 is allowed to be rotated by the rotary motor130. Other construction of this apparatus is substantially the same asthe above described plating apparatus according to the first embodiment.

[0143] As described above, when a plating current flows, an electriccurrent value on an inner central side of a substrate W is smaller thanan electric current value on an outer peripheral side of the substratedue to a difference in sheet resistance of the substrate W. Ifenergization time of the plating current can be made longer on the innercentral side of the substrate W than on the outer peripheral side, itbecomes possible to make a product of the electric current value and theenergization time substantially equal to that of the inner central sideand the outer peripheral side of the substrate W. Since film thicknessof a plated film formed on a surface of substrate W is proportional tothe product of the electric current value of the plating current and theenergization time of the plating current, making the product equal asdescribed above can provide a plated film having a uniform filmthickness over an entire surface of the substrate.

[0144] According to the plating apparatus of this embodiment, adjustmentof the energization time of the plating current, which realizesformation of a plated film having a uniform film thickness, is made bymaking the area of the anode 98 smaller than the area of the substrateW, and by driving the rotary motor 46 as a substrate-rotating device(see FIG. 4) to rotate substrate holder 36 together with the substrate Wduring a plating process. Thus, when the substrate W is rotated, pointP1 shown in FIG. 22, situated on an inner central side of the substrate,always faces the anode 98 and causes electric current to flowtherethrough. On the other hand, with regard to point P2 situated on anouter peripheral side of the substrate, this point faces the anode 98when it moves (rotates) along solid line F, but it does not face theanode 98, and electric current does not flow therethrough, when thepoint moves (rotates) along broken line G Accordingly, the energizationtime of the electric current becomes longer at point P1 than at pointP2.

[0145] According to this embodiment, the energization time of theelectric current on the inner central side of the substrate W is thusmade longer than that on the outer peripheral side of the substrate byproperly selecting shape, size, area and positioning of the anode 98 ,along with rotational speed of the substrate W, thereby making a productof the plating current value and the energization time of the platingcurrent equal over an entire surface of the substrate W, whereby aplated film having a uniform film thickness can be formed. In addition,since the area of the anode 98 is made smaller than the area of thesubstrate W, it becomes possible to utilize a surface of the substrate Wnot facing the anode 98, i.e. an exposed surface of the substrate, toconduct an optical film-thickness measurement or the like simultaneouslywith formation of the plated film.

[0146] The cross-sectional area of the anode 98 is selected, asdescribed above, so that a film thickness of the plated film may be madeuniform over the entire surface of the substrate, and is preferablyselected from the range of 25-95% of the area of the surface ofsubstrate W. When the anode 98 is of a disc shape, if thecross-sectional area of the anode 98 is less than 25% of thecross-sectional area of the substrate, i.e. the diameter of the anode 98is smaller than the radius of the substrate W, there should be a portionin the vicinity of a center of the surface of the substrate W thatcannot be plated. Rotational speed of the substrate W is preferably 3-60revolutions per minute, more preferably 5-40 revolutions per minute.

[0147] A plating treatment may be carried out while rotating the anode98 by driving the rotary motor 130 as an anode-rotating device.Alternatively, plating may be carried out while the rotary motor 130 isstopped and the anode 98 is kept stationary. When plating is conductedwhile rotating the anode 98, a rotating direction of the anode 98 may bethe same as, or opposite to, a rotating direction of the substrate W;however, it is preferred to rotate the anode 98 in the same direction asthe substrate. A rotational speed of the anode is preferably 3-60revolutions per minute, more preferably 5-40 revolutions per minute.

[0148] The anode 98 may be of any shape insofar as a uniform plated filmthickness over an entire substrate surface can be obtained, and can be,for example, an oval or a heart-like shape.

[0149]FIG. 23 is a plan view of electrode arm 30 of a plating apparatusaccording to a third embodiment of the present invention. Constructionof the plating apparatus of this embodiment is fundamentally the same asthe above plating apparatus according to the second embodiment. A groove130 a is formed along a length of the electrode arm 30 of thisapparatus. Further, rotary motor 130 as an anode-rotating device mountedon an upper end of electrode portion 28 is designed to function also asan anode-translating device. Thus, by actuation of the rotary motor 130,anode 98 can translate in a direction of arrow H shown in FIG. 24. Sinceother construction is the same as the apparatuses of the above describedembodiments, description thereof is herein omitted.

[0150] While the plating apparatus of this embodiment operates in thesame manner as the plating apparatus of the second embodiment, in thecase of this apparatus, simultaneously with rotating of substrate W byrotary motor 64 (see FIG. 4) during a plating process, the anode 98 istranslated in the direction of arrow H, shown in FIG. 24, by the rotarymotor 130 that functions also as an anode-translating device.Translational speed of the anode 98 is preferably 5-40 reciprocationsper minute.

[0151] Though the above-described second and third embodiments show acase where a substrate-rotating device allows the substrate to rotateabout its central axis, the device may be designed to allow thesubstrate to revolve eccentrically. It is also possible to design thesubstrate-rotating device so that the device itself can make a scrollingmovement relative to anode 98.

[0152]FIG. 25 is a pattern diagram illustrating a relationship betweensubstrate W and electrode portion 28 of a plating apparatus according toa fourth embodiment of the present invention.

[0153] Though construction of the plating apparatus of this embodimentis fundamentally the same as the above-described apparatuses, it differsin that anode 98 of the electrode portion 28 is inclined relative tosubstrate W, as shown in FIG. 25. Since other construction of thisapparatus is the same as the above-described first embodiment,description thereof is herein omitted.

[0154] As shown in FIG. 25, the anode 98 is inclined so that a distancebetween the anode and the substrate W is small on an inner central sideof the substrate W and large on an outer peripheral side of thesubstrate W. An angle of inclination, i.e. angle a shown in FIG. 25, ispreferably not more than 30°. By inclining the anode 98 in this manner,resistance R2 of a plating liquid, described above referring to FIG. 30,is made smaller on the inner central side of the substrate and larger onthe outer peripheral side of the substrate, whereby an electric currentvalue is made more equal on the inner central side of the substrate tothat on the outer peripheral side of the substrate. Thus, in addition toadjustment of the energization time of the plating current according tothe second embodiment, electric current values at various points of thesubstrate can also be adjusted, thereby making a product of the time forpassing electric current and the electric current value equal over anentire surface of the substrate, whereby a film thickness of a platedfilm formed on the substrate W can be made uniform over the entiresurface of the substrate W.

[0155] Preferably, a minimum distance between the anode 98 and thesubstrate W, i.e. a distance between the anode and a central portion ofthe substrate W, is in the range of 2-65 mm. Plating liquid impregnationmaterial 110 should preferably have a thickness of 2-15 mm. It is alsopossible to make a cross-sectional size of the anode 98 substantiallythe same as that of the substrate W, and design a combination of theanode 98 and the plating liquid impregnation material 110 as shown inFIG. 26, viz. a symmetrical configuration about a central axis of thesubstrate. In this case, the above-described adjustment of energizationtime of the electric current is not necessary, and formation of a platedfilm having a uniform film thickness can be achieved merely byadjustment of electric current value.

[0156]FIG. 27A is a pattern diagram illustrating a relationship betweensubstrate W and anode 98 at initiation of a plating process in a platingapparatus according to a fifth embodiment of the present invention, andFIG. 27B is a pattern diagram illustrating a relationship betweensubstrate W and anode 98 at completion of the plating process in theplating apparatus according to the fifth embodiment of the presentinvention. FIG. 28A and FIG. 28B are equipotential diagrams showing astate of electric field between the anode 98 and the substrate W in therelationships of FIG. 27A and FIG. 27B, respectively.

[0157] Though construction of the plating apparatus of this embodimentis basically the same as the above-described first embodiment, itdiffers in that motor 54 (see FIGS. 8 and 9) for vertical movementfunctions as a device for changing a distance between the anode 98 andthe substrate W (as a pulling-away device), as shown in FIGS. 27A and27B.

[0158] While the plating apparatus of this embodiment operates in thesame manner as the plating apparatus of the first embodiment, in thecase of this apparatus, a distance between the anode 98 and thesubstrate W is changed, during a period between initiation of plating(FIG. 27A) and completion of plating (FIG. 27B), by motor 54 functioningas a pulling-away device. Thus, at the initiation of plating (FIG. 27A),a distance between the anode 98 and the substrate W is set preferably inthe range of 2-18 mm. While keeping this distance, a plated film with athickness of about 100 nm is formed on a surface of the substrate W.Thereafter, plating treatment is continued while a distance between theanode 98 and the substrate W is made larger by pulling the electrodeportion 28 upwardly by motor 54. The plating treatment is completed whena desired plated film thickness is obtained (FIG. 27B). A distancebetween the anode 98 and the substrate W is preferably in the range of3-50 mm.

[0159] Since a distance between the anode 98 and the substrate W issmall at initiation of plating, a potential gradient is higher on aninner central side of substrate W than that on an outer peripheral sideof the substrate, as shown in FIG. 28A. Accordingly, an electric currentvalue is higher on the inner central side of the substrate W than on theouter peripheral side, whereby a larger amount of plated film is formedon the inner central side of the substrate W. When a plated film is thusformed on the surface of the substrate W, a sheet resistance value at aportion of the substrate where a plated film is formed in a largeramount, i.e., the inner central portion of the substrate W, becomeslower. If plating is continued, a plated film becomes much more thick onthe inner central side of the substrate. In view of the above, adistance between the anode 98 and the substrate W is made larger, duringa plating process, according to this embodiment.

[0160] When a distance between the anode 98 and the substrate W is madelarger, as shown in FIG. 28B, a potential gradient on an outerperipheral side of substrate W becomes higher than that on an innercentral side of the substrate, whereby an electric current value becomeslarger on the outer peripheral side of the substrate W than on the innercentral side. Thus, contrary to the case of FIG. 28A, a larger amount ofplated film is formed on the outer peripheral side of the substrate W.Therefore, as a result of transition from the state of FIG. 27A to thestate of FIG. 27B, in accordance with this embodiment, film thickness ofplated film can be finally made uniform over an entire surface of thesubstrate.

[0161] When the electrode portion 28 is pulled upwardly, it may bepulled up slowly, taking a considerable time, or quickly, taking littletime.

[0162] The embodiments of the present invention as hereinabove describedare but illustrative examples, and the present invention is not limitedthereto. It will be understood that many changes and modifications maybe made to the above embodiments without departing from the spirit ofthe present invention. It will, therefore, be understood that theabove-described embodiments, in combinations thereof, may be practicedwithin the scope of the present invention.

[0163] Though plating apparatuses of a substrate-immersing type, inwhich plating and treatments incidental thereto can be conducted in asingle unit, are described hereinabove, the present invention is notlimited to such a type but is applicable to any type of platingapparatuses, including a face-down type and a face-up type. As anexample, a plating apparatus of a face-down type, to which a seventhembodiment of the present invention is applied, is shown in FIG. 29.

[0164] The plating apparatus shown in FIG. 29 has a substrate holder 200for detachably holding a substrate W with its surface, to be plated,facing downwardly. A disc-shaped anode 202 (having a smallercross-sectional size than the substrate W), which is eccentric to thesubstrate W, is disposed at a bottom of a substantially cylindricalplating tank 201. A rotary motor 203 as an anode-rotating device isprovided beneath the anode 202. Further, a rotary motor 205 as asubstrate-rotating device is mounted on an upper portion of a frame 204that supports the substrate holder 200. By thus providing theanode-rotating device 203 and the substrate-rotating device 205, itbecomes possible, as with the above-described plating apparatuses of asubstrate-immersing type, to make energization time of an electriccurrent on an inner central side of substrate W longer than that on anouter peripheral side of the substrate, whereby a plated film having auniform film thickness can be formed.

[0165] As described hereinabove, according to the present invention, aportion of a substrate facing an anode is moved in such a state that aninner central portion of a surface of the substrate faces the anode fora longer time than does an outer peripheral portion of the surface ofthe substrate, thereby making energization time of a plating current tothe inner central portion of the surface of the substrate longer thanenergization time of a plating current to the outer peripheral portionof the surface of the substrate, whereby products of the electriccurrent values and the energization times of the electric current atvarious points of the substrate can be made equal over an entire surfaceof the substrate. Consequently, it becomes possible to make a filmthickness of plated film formed on the substrate uniform over the entiresurface of the substrate.

[0166] Further, by making a distance between the anode and the innercentral portion of the substrate smaller than the distance between theanode and the outer peripheral portion of the substrate, resistance of aplating liquid can be made smaller at the inner central portion of thesubstrate and larger at the outer peripheral portion of the substrate.This can make the electric current value more equal at the inner centralportion of the substrate to that at the outer peripheral portion,whereby a film thickness of a plated film formed on the substrate can bemade uniform over an entire surface of the substrate.

[0167] Further according to the present invention, a distance between asubstrate and the anode can be changed after initiation of plating.Since a potential gradient is higher on an inner central side of asubstrate than an outer peripheral side of the substrate at initiationof plating, a larger amount of plated film is formed on the innercentral side of the substrate. This situation can be reversed by latermaking a distance between the anode and the substrate larger, whereby aplated film having a uniform film thickness over an entire surface ofthe substrate can be obtained.

[0168] The above and other objects, features, and advantages of thepresent invention will be apparent from the following description whentaken in conjunction with the accompanying drawings which illustratepreferred embodiments of the present invention by way of example.

What is claimed is:
 1. A plating method, comprising: disposing asubstrate and an anode in such a state that the substrate faces saidanode; flowing a current between the substrate and said anode whilesupplying a plating liquid therebetween; and moving a portion of thesubstrate facing said anode in such a state that an inner centralportion of the surface of the substrate faces said anode for a longertime than an outer peripheral portion of the surface of the substratefaces said anode.
 2. The plating method according to claim 1, whereinthe portion of the substrate facing said anode is moved by rotation ofthe substrate.
 3. The plating method according to claim 1, wherein theportion of the substrate facing said anode is moved by rotation of saidanode.
 4. The plating method according to claim 1, wherein the portionof the substrate facing said anode is moved by translation of saidanode.